Apparatus for spraying liquids, and disposable containers and liners suitable for use therewith

ABSTRACT

A spray gun ( 1 ) has a fluid reservoir ( 11 ) with a removable liner ( 13 ) received in a container ( 12 ) having a detachable lid ( 15 ). The liner ( 13 ), which may be thermo/vacuum-formed from a planar material, has a shape that corresponds to and is a close fit within the interior of the container ( 12 ) and collapses as fluid is withdrawn from within the liner ( 13 ) during operation of the spray gun ( 1 ). The lid ( 15 ) has an outlet ( 16 ) connected to an inlet on the spray gun ( 1 ) for transfer of liquid from the reservoir ( 11 ) to the spray gun ( 1 ) and the container ( 12 ) has a vent ( 12 A) in the base end for admitting air between the container ( 12 ) and the liner ( 13 ) as liquid is withdrawn from within the liner ( 13 ).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of pending prior U.S. Ser. No.10/881,291, filed Jun. 30, 2004; which was a continuation of U.S. Ser.No. 09/508,883, filed Jul. 23, 1999, now U.S. Pat. No. 6,820,824 nowissued; which was a national stage filing under 35 U.S.C. 371 ofPCT/US98/00796, filed Jan. 14, 1998, which International Application waspublished by the International Bureau in English on Jul. 30, 1998; whichclaims priority to GB 9701447.6, filed Jan. 24, 1997, and GB 9712784.9,filed Jun. 18, 1997; the disclosure of which is herein incorporated byreference.

The present invention relates to containers, more especially, disposablecontainers and to containers which can function as liners. The inventionalso relates to apparatus for spraying liquids (for example, spray guns)and, more especially, to the liquid containers or reservoirs of suchapparatus.

There are many uses, in many different fields, for disposablecontainers. For example, many goods are packaged in disposablecontainers (e.g. bags) either before or after purchase. When thedisposable container is a plastic bag, it will often be re-used by thepurchaser as a disposable liner for another receptacle, for example arefuse bin. In some cases, disposable liners are produced specificallyfor use in other, re-usable, receptacles: in those cases, the liner maybe intended to aid disposal of the contents of the receptacle (as in thecase of a liner in a refuse bin); to protect the receptacle or itscontents; or to facilitate, or even eliminate, the cleaning of thereceptacle.

The use of a liner in a receptacle in which a substance like glue, paintor plaster is mixed or contained for use can be particularlyadvantageous, in terms of facilitating the cleaning of the receptacleafter use and of preventing substances in the receptacle from beingcontaminated by the remains of other substances. Receptacles in whichpaints are mixed or contained for use, for example, must be clean toensure that the colour or quality of the paint is not altered by tracesof other substances: that is particularly important, as explained above,when a vehicle is being re-painted and the paint is required to match anexisting one. To avoid contamination problems when mixing paints, it isoften the practice in vehicle body shops to use disposable waxed papercups as mixing containers, particularly when only a small amount ofpaint is required. An alternative approach, proposed in U.S. Pat. No.4,383,635, involves the provision of a disposable container which, foruse, is located in a re-usable frame-like receptacle.

In the field of spray guns, it has been proposed for various reasonsthat a disposable liner should be used in the reservoir of the gun (seeU.S. Pat. Nos. 3,211,324, 3,255,972, 4,151,929, 4,951,875 and 5,143,294,and EP-A-0 678 334). Guns for spraying liquids (e.g. paints, gardenchemicals etc.) are generally well known and typically comprise areservoir in which a liquid to be dispensed is contained, and a spraynozzle through which the liquid is dispensed, under pressure, under thecontrol of a trigger mechanism. The liquid may be fed from the reservoirunder gravity and/or it may be entrained in a stream of pressurizedfluid, for example air or water, which is supplied to the gun from anexternal source.

When a user wishes to change the liquid in the reservoir of a spray gun,it is usually necessary to clean the gun very thoroughly to ensure thatno traces of the old liquid remain in the gun to contaminate the newliquid. That applies particularly to paint spray guns because any tracesof an old batch of paint remaining in a gun may affect the colour of anew batch of paint to the extent that the new batch of paint becomesuseless. This can cause problems especially in vehicle body shops wherethe paint applied to a vehicle is often required to match existing paintwork exactly. Alternatively, if paint residues have been allowed to drywithin the gun, they may flake and contaminate the new batch of paint.The cleaning of spray guns is, however, a comparatively complex and timeconsuming operation. Moreover, in the case of paint spray guns, thecleaning operation involves the use of comparatively large amounts ofsolvents which, for environmental reasons, should be handled anddisposed of with care. That, in turn, can add substantially to the costof a painting operation. It has already been suggested (see, forexample, EP-A-0 678 334 mentioned above) that the use of a disposableliner in the paint reservoir (i.e. the paint pot) of a spray gun cansimplify the cleaning of the gun and reduce the amount of solventrequired.

The present invention is concerned with the provision of a containerwhich is sufficiently inexpensive to be disposable and which canpreferably be collapsed when it is to be disposed of but which,nevertheless, is comparatively easy to handle and to fill when in use.The invention is concerned, more especially, with the provision of sucha container which is suitable for use as a liner in another receptacle.The present invention is also concerned with enabling the cleaning ofspray guns and like apparatus to be simplified, and with therebyenabling the time and expense associated with that operation to bereduced.

The present invention provides a container comprising side walls and acomparatively-rigid base thermo/vacuum-formed from a plastics material;wherein the side walls are thin in comparison to the base and arecollapsible, but the container is capable of standing, unsupported, onthe base with the side walls extended and upright.

More especially, the present invention provides a container comprising abase, and side walls extending from the base; wherein the base and sidewalls are thermo/vacuum formed together from a plastics material in sucha manner that the base is comparatively rigid and the side walls arethin in comparison to the base and are collapsible but the container iscapable of standing unsupported, on the base with the side wallsextended and upright.

A container in accordance with the invention may be used as a liner fora receptacle, the liner having a shape which corresponds to the interiorof the receptacle. As a modification, the invention also provides, incombination with a receptacle, a disposable liner which fits within andhas a shape corresponding to the interior of the receptacle wherein theliner is thermo/vacuum formed from a plastics material. The liner ispreferably, but not necessarily, collapsible.

The present invention also provides a spray gun comprising a fluidreservoir; a removable, collapsible, liner which has a shapecorresponding to, and is a close fit within, the interior of thereservoir; and a spray nozzle for dispensing fluid from within theliner; wherein the liner collapses when fluid is withdrawn from withinthe liner during operation of the gun.

Also in accordance with the invention, there is provided a spray guncomprising a fluid reservoir having a removable lid located in anopening in the reservoir; a removable liner located within the reservoirand secured to the reservoir, by the lid, at the periphery of theopening; and a spray nozzle for dispensing fluid from within the liner;wherein the liner is removable from the reservoir together with the lid.

The present invention also provides a gravity-fed spray gun comprising afluid reservoir having a removable lid located in an opening in thereservoir; and a spray nozzle for dispensing fluid drawn from within thereservoir through an outlet in the lid; wherein the reservoir isremovable from the gun and is capable of standing on its own to enablefluid to be loaded into the reservoir through the opening.

The invention further provides a spray gun comprising a fluid reservoir;and a spray nozzle for dispensing fluid from within the reservoir; thereservoir comprising a self-supporting container which is removable fromthe gun and is collapsible for disposal.

In accordance with another aspect of the invention, there is provided afluid reservoir for attachment to a spray gun, the reservoir having aremovable lid which is located in an opening in the reservoir and inwhich is formed a fluid outlet for the reservoir; the reservoirincluding a removable, collapsible, liner which has a shapecorresponding to, and is a close fit within, the reservoir; wherein theliner is secured to the reservoir by the lid at the periphery of theopening and is removable from the reservoir together with the lid. Theinvention also provides a fluid reservoir for attachment to a spray gun,the reservoir having a removable lid which is located in an opening inthe reservoir and in which is formed a fluid outlet for the reservoir,the fluid outlet being shaped for attachment to the spray gun; and aclosable air vent in the end of the reservoir remote from the lid.

In accordance with yet another aspect of the invention, there isprovided a liner for use in the reservoir of a spray gun, the linerbeing formed from a plastic material and being a close fit within thereservoir; the liner having a comparatively rigid base, and side wallswhich are thin in comparison to the base and are collapsible.

The present invention also provides a spray gun comprising a fluidreservoir, and a spray nozzle for dispensing fluid from within thereservoir, the reservoir having a removable lid and including aremovable, generally conical, mesh filter secured in the reservoir bythe lid.

The present invention also provides a gravity-feed spray gun comprisinga fluid reservoir, and a spray nozzle for dispersing fluid from withinthe reservoir, the reservoir having a removable lid and a removableliner secured in the reservoir by the lid.

The term “thermo/vacuum-forming” as used herein means a process by whicha sheet of material is heated to a softened condition and formed into arequired shape, defined by a mould, while in that softened condition. Itincludes the case in which the application of a differential airpressure is used to assist in forming the material into the requiredshape and, in particular, includes the case in which a vacuum isproduced on one side of the material to assist in forming it into therequired shape (also known simply as “vacuum-forming”).

The term “collapsible” as used herein with reference to the side wallsof a container/liner in accordance with the invention indicates that theside walls can be distorted so that, by the application of moderatepressure (e.g. hand pressure), the rim of the container can be pushedtowards the base of the container, without the side walls beingruptured.

The term “paint” is used herein to include all forms of paint-likecoating materials that can be applied to a surface using a spray gun,whether or not they are intended to colour the surface. The termincludes, for example, primers, base coats, lacquers and similarmaterials.

By way of example only, embodiments of the invention will be describedwith reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a prior art spray gun, shownpartly-disassembled so that it can be filled with paint;

FIG. 2 shows the components of an alternative form of paint reservoirfor the gun of FIG. 1, in an exploded condition;

FIG. 3 shows the paint reservoir of FIG. 2 in an assembled condition,with an adapter for connecting the reservoir to a spray gun;

FIG. 4 shows a longitudinal cross-section through the paint reservoirand the adapter of FIG. 3;

FIG. 5 shows the paint reservoir of FIG. 4 being attached to a spraygun;

FIG. 6 shows the paint reservoir of FIG. 4 in use on a spray gun;

FIG. 7 shows components of the paint reservoir of FIG. 4 being removedafter use;

FIG. 8 is similar to FIG. 2 but shows a modified form of paintreservoir;

FIG. 9 shows a longitudinal cross-section through an alternative form oflid for the paint reservoirs of FIGS. 2 to 4 and 8;

FIG. 10 is similar to FIG. 2 but shows another modified form of paintreservoir;

FIG. 11 shows part of a longitudinal cross-section through the paintreservoir of FIG. 10;

FIG. 12 shows a spray gun similar to that of FIG. 1 but with analternative form of paint reservoir;

FIG. 13 shows the gun of FIG. 12 with a modified form of paintreservoir;

FIG. 14 illustrates a modification to the reservoir of the gun of FIG.13.

FIG. 15 is a view, similar to FIG. 3, of an alternative form of paintreservoir;

FIGS. 16 and 17 show modified forms of a component of FIG. 15;

FIG. 18 illustrates the use of a holder for the paint reservoir of FIG.15;

FIG. 19 is a perspective view of a liner/container in accordance withthe invention;

FIG. 20 is a similar view but showing the liner/container in the processof being collapsed for disposal;

FIG. 21( a) to (c) is a diagrammatic illustration of a method forproducing a liner for the paint reservoirs of FIGS. 2 to 4, and 10;

FIG. 22 illustrates a modification of the method of FIG. 21;

FIG. 23 shows a paint-mixing pitcher; and

FIG. 24 shows a liner in accordance with the invention, for use with thepitcher of FIG. 23.

FIG. 1 of the drawings illustrates a typical prior art paint spray gun 1of the gravity-feed type. The gun 1 comprises a body 2, a handle 3 whichextends downwards from the rear end of the body, and a spray nozzle 4 atthe front end of the body. The gun is manually-operated by a trigger 5which is pivotally-mounted on the sides of the gun. The paint reservoir,or paint pot, 6 which contains paint (or similar material) to bedischarged by the gun, is located on the top of the body 2 andcommunicates with an internal passageway (not visible) for compressedair, which extends through the gun from a connector 7 at the lower endof the handle 3 to the nozzle 4. In use, the connector 7 is connected toa source of compressed air (not shown) so that, when the user pulls onthe trigger 5, compressed air is delivered through the gun to the nozzle4 and entrains and atomizes paint which is being delivered under gravityfrom the pot 6. The paint is then discharged through the nozzle 4 withthe compressed air, as a spray.

The paint which is contained in the pot 6 is often mixed by hand (forwhich a separate receptacle, for example a jug, is required), and pouredinto the pot. To ensure that there are no unwanted particles in thepaint, which would spoil the finish of the painted surface, the paint isusually poured into the pot 6 through a filter. FIG. 1 shows the cap 8of the pot 6 removed for this purpose, and a conical filter 9 about tobe positioned on the open end of the pot. The filter 9 is shown as beinga known type of disposable conical filter, having solid sides and afilter mesh portion 10 at the pointed end of the cone. When the pot 6has been filled with paint, the filter 9 is removed and discarded, andthe cap 8 of the pot is replaced. If the filter 9 is a reusable filterthen, like the gun, it should be cleaned thoroughly before it is usedwith a different liquid (e.g. a paint of a different colour or a liquidhaving a different chemical composition).

FIG. 2 illustrates the components of an alternative form of paint pot 11which can be used on the gun 1 of FIG. 1 (or any similar gun) instead ofthe pot 6. The alternative form of paint pot 11 is shown assembled inFIG. 3 and (in cross-section) in FIG. 4.

The paint pot 11 comprises an open container 12, comparable in size to aconventional paint pot of a hand-held spray gun, having an air hole 12Ain its base and provided with a disposable liner 13. The liner 13corresponds in shape to (and is a close fit in) the interior of thecontainer 12 and has a narrow rim 14 at the open end which sits on thetop edge of the container. The container 12 also has a disposable lid 15which is a push-fit in the open end of the liner 13. The lid 15 has acentral aperture 16 (FIG. 4) from which extends a connector tube 17provided, at its end, with outward extensions 18 forming one part of abayonet connection. The aperture 16 is covered by a filter mesh 19 whichmay be a push fit into the aperture or may be an integral part of thelid 15. The lid 15 is held firmly in place on the container 12 by anannular collar 20 which screws onto the container, on top of the lid.

The paint pot 11 is attached to the spray gun 1 through the use of anadapter 21 shown, separated from the paint pot, in FIG. 3 and (incross-section) in FIG. 4. The adapter 21 is a tubular component which,at one end 22, is formed internally with the other part of the bayonetconnection for attachment to the connector tube 17 of the paint pot 11.At the other end 23, the adapter is shaped to match the standardattachment of the spray gun paint pot (typically a screw thread).

The liner 13 of the paint pot 11, as already mentioned, corresponds inshape to the interior of the container 12 and has a narrow rim 14 at theopen end which sits on the top edge of the container. As describedbelow, the liner is self-supporting but is also collapsible and,preferably, has a comparatively rigid base 13A and comparatively thinside walls 13B so that, when it collapses, it is in the longitudinaldirection by virtue of the side walls collapsing rather than the base.In addition, the liner 13 has no pleats, corrugations, seams, joints orgussets, and also no groove at the internal junction of the side walls13B with the base 13A. A liner of that type will be described in greaterdetail later with reference to FIGS. 19 and 20. Also described below isa thermo-forming process by which such a liner can be produced.

The container 12 of the paint pot 11 is formed from a plastic material,for example polyethylene or polypropylene, and may be translucent (asshown in FIG. 2) or opaque, and of any suitable size. For use with apaint spray gun, containers having a capacity of 250, 500 or 800 mlcould typically be used, although other sizes could be used if required.The lid 15 is also formed from a plastic material, for example,polyethylene or polypropylene, and may be formed by an injectionmoulding process. The lid may be translucent or opaque and may becoloured. The collar 20 may be a moulded plastic component, or it may bea machined metal (for example, aluminum) component. The adapter 21 maybe a machined metal component and may, for example, be formed fromaluminum and anodised.

To use the paint pot 11, the adapter 21 is attached (at the end 23) tothe spray gun and is left in position. Then, with the paint pot 11disassembled as shown in FIG. 2, the liner 13 is pushed inside thecontainer 12. Paint is then put into the container, the lid 15 is pushedinto place and the collar 20 is screwed down tightly to hold the lid inposition. The top portion of the liner 13 is then trapped between thelid 15 and the container 12, and the liner rim 14 is trapped between thetop edge of the container and the collar 20, as shown in FIG. 4.Advantageously, the lid 15 is formed with barbs (not visible) on itssurface to engage and hold the top of the liner. The spray gun 1 is theninverted from its normal operating position so that the end of theconnector tube 17 can be attached to the adapter 21 as illustrated inFIG. 5, after which the gun can be returned to its normal position(illustrated in FIG. 6) and is ready for use in the usual way. As paintis removed from within the liner 13, the sides of the liner collapse asa result of the decreased pressure within the liner. The base of theliner, being more rigid, retains its shape so that the liner tends tocollapse in the longitudinal rather than the transverse directionthereby reducing the possibility of pockets of paint being trapped inthe liner.

The user can choose to evacuate the air from within the liner 13 beforeoperating the spray gun 1 although that is not essential. It does,however, increase the range of angles at which the gun will functionsatisfactorily since there is no risk of air entering the gun from thepaint pot 11. To evacuate the air from within the liner 13, the trigger5 of the gun should be actuated while the gun is still in the positionshown in FIG. 5.

After use, when the gun is to be cleaned, the gun can be re-inverted andthe trigger 5 can be actuated briefly to allow paint within the gun todrain back into the liner in the pot 11. The pot 11 is then removed fromthe gun by detaching the connector tube 17 from the adapter 21 (whichremains on the gun). The collar 20 is removed from the container 12, andthe lid 15 is then pulled out, bringing with it the collapsed liner 13,as shown in FIG. 7. The lid (including the filter 19) and liner arediscarded, leaving the container 12 and collar 20 clean and ready forre-use with a fresh liner and lid. Only the gun itself needs to becleaned, resulting in a substantial reduction in the amount of solventused. The risk of unused paint spilling from the pot 11 is alsosubstantially reduced because the liner 13 is removed and discarded withthe lid 15 in place. Moreover, because the liner is discarded in acollapsed condition, the amount of space required for collection of usedliners is minimized.

Because the liner 13, as described above, is an accurate fit inside thecontainer 12 and has a smooth internal surface, it is possible to mixpaint in the container 12 itself rather than in a separate receptacle.In that way, cleaning of a separate mixing receptacle can be eliminatedto achieve a further reduction in the amount of solvent used. Thatpossibility does not exist when using a gravity-feed gun with aconventional paint pot, as shown at 6 in FIG. 1, because the latter isopen at both ends. The possibility of the liner 13 being punctured ordamaged by the mixing implement is minimized, first because the linerfits inside the container 12 exactly and, second, because theself-supporting nature of the liner (described below) means that it isless likely to be dragged around inside the container during the mixingprocess. To facilitate the use of the container 12 as a mixingreceptacle, the side walls of the container may be provided withmarkings 25 (FIGS. 2 and 3) enabling the volume of the contents of thecontainer to be determined. The general shape of the container 12 and,in particular, the fact that it is flat-bottomed and stable when in theorientation shown in FIG. 2 makes it particularly suitable for use as amixing receptacle, as does the fact that it is translucent as alreadydescribed. If, however, the container 12 is opaque, it could be formedwith slots in the side walls, through which the liner 13 could be viewedto enable the user of the spray gun to assess the amount of paint in thepot 11 at any time.

When paint is mixed in the container 12, the inclusion of the filtermesh 19 in the container lid 15 prevents unwanted particles in the paintfrom entering the spray gun. The mesh 19 can be omitted, however, if thepaint is textured, or if it is mixed in a separate receptacle andstrained when it is transferred to the lined container 12 or if thepresence of contaminants in the paint is unimportant.

Although the collar 20 of the paint pot 11 is described above as being aseparate item, it could be combined with the lid 15, in which case itwould also be disposable. As a further alternative, the lid 15 (with theconnector tube 17 and the mesh 19) could be formed as an integral partof the liner 13, to which it could be connected by a hinge joint 26 asillustrated in FIG. 8. In that case, there is no need for the lid to fitinside the mouth of the liner to ensure that the lid and liner will beremoved together from the container after use: however, that would stillbe necessary if the lid were required to remain in place in the linerafter use. As yet another alternative, the collar 20 could be replacedby a band secured around the top of the pot 11 to hold the lid 15 andliner 13 in place. The band could be secured to the pot 11 and could,for example, be formed from rubber or be part of a metal cliparrangement of the type used to secure the tops of jars and bottles.

If a more positive engagement is required between the lid 15 of FIGS. 2to 4 and the liner 13, the lid could be a snap fit with the linerinstead of a push-fit as shown. The liner could, for example, be formedwith an internal circumferential rib positioned to engage in acorresponding groove on the adjacent surface of the lid.

As yet a further alternative, the push-in lid 15 could be replaced by alid 27 having the form shown in FIG. 9. The lid 27 is also a push-fitinside the liner but is generally conical in shape and at its upper end28, corresponds in shape to the end of the connector tube 17 of FIGS. 2to 4 so that it will engage in the same adapter 21. The lid 27 has anoutwardly-extending rim 29 which will sit on top of the liner rim 14,and a shaped portion 29A which will engage the internal surface of theliner. The form of the shaped portion 29A allows the lid 27 to be pushedinto the mouth of the liner and also provides a recess 29B into whichthe edge of the liner can contract so that the lid is securely located.The form of the shaped portion illustrated in FIG. 9 is not essential,however, and alternatives could be used including, for example, barbs asdescribed above with reference to the lid 15 of FIG. 4. The lid 27 isheld in place on the container by a screw-on collar, similar to thecollar 20, which will sit on top of the rim 29 of the lid. The lid 27may incorporate a filter similar to the filter 19 of FIGS. 2 to 5.Alternatively, in each case, the filter may be generally cylindrical inshape so that it can be inserted into the tubular part of the lid fromthe end adjacent the bayonet connection. In that case, the internalshaping of the tubular part of the lid should ensure that the filterremains in position when the spray gun is in use.

The components of an alternative form of paint pot 30 are illustrated inFIG. 10. The pot 30, like the pot 11 of FIG. 2, comprises a container 12and a liner 13. In this case, however, the filter 19 of the pot 11 isformed as a separate item 31 having a diameter corresponding to that ofthe container 12 and including a circumferential sealing gasket 32. Inaddition, the lid 15 and collar 20 of the pot of FIG. 2 are replaced bya generally-conical lid 33 which is a screw-fit onto the container andwhich, at its upper end has a tubular extension 34 of similar shape tothe connector tube 17 of FIG. 3 so that it will engage in the sameadapter 21. The pot 30 is assembled by pushing the liner 13 inside thecontainer 12 and then, after paint has been put into the container,placing the filter 31 on top of the container and securing it inposition by screwing down the lid 33. The rim 14 of the liner 13 and thesealing gasket 32 of the filter 31 are then both trapped between the lid33 and the container 12, as illustrated in FIG. 11, thereby preventingthe leakage of paint from the pot 30 at this location when the pot hasbeen secured to a spray gun and is inverted for use.

The adapter 21 could be dispensed with by forming the ends of thetubular parts 17, 34 of lids of the containers 11, 30 with screw threadsso that they can engage directly in the standard paint pot attachment onthe spray gun 1.

FIG. 12 illustrates an alternative spray gun in which the standard paintpot 6 of the spray gun 1 (see FIG. 1) is retained and is provided with aliner 35 which fits inside the pot and, preferably, extends into theconnection with the body 2 of the gun to form a liquid-tight seal withthe latter, for example through the use of a flexible O-ring (notvisible) between the gun and the liner. In this case, the liner 35 doesnot collapse when paint is removed from within the pot and may be formedfrom a more rigid material to assist in positioning it within the pot 6.Once in position, the liner 35 is held in place by the cap 8 which isscrewed down onto an outwardly-extending rim 36 at the open end of theliner. The pot 6 of FIG. 12 is additionally provided with a filter 37which is of generally conical shape and formed entirely of mesh materialand which, in use, is positioned inside the liner 35. The filter 37,like the liner 35, has an outwardly-extending rim 38 which lies on topof the liner rim 36 and is likewise held in place by the cap 8 of thepot 6.

The pot 6 of FIG. 12, unlike the pot 11 of FIG. 3 is intended to befilled with paint while attached to the spray gun 1. The liner 35 andfilter 37 are placed in position, paint is poured into the pot, and thecap is fitted. During this operation, there is no risk of the filterbeing dislodged and, because the filter is formed entirely of meshmaterial, the user is always able to see the paint level while the paintis being poured into the pot. The gun 1 is then ready for use. All ofthe paint dispensed by the gun passes through the filter 37 and thereis, accordingly, no need for the paint to be filtered when it is beingpoured into the pot 6. After use, the cap 8 unscrewed is to allow thefilter 37 and liner 35 to be removed. The liner 35 is discarded and thefilter 37 is either also discarded or is cleaned, depending on whetheror not it is disposable. The use of the liner 35 again reduces theamount of solvent required to clean the gun 1, with a further reductionbeing possible through the use of a disposable filter 37.

The filter 37 can have any suitable shape and may, for example, havefluted sides to increase the effective surface area of the filter.

In a modified arrangement, illustrated in FIG. 13, the liner 35 and thefilter 37 are combined to form a single unit 39. In this case, thefilter is discarded with the liner.

In each of the arrangements shown in FIGS. 12 and 13, the liner 35 andfilter 37 can be removed from the pot 6 with the lid 8. In that case, itis possible to replace the conventional lid 8 of the pot 6 by adisposable lid so that the lid 8, liner 35 and filter 37 can bediscarded together.

The disposable unit 39 of FIG. 13 could be modified so that it wouldreplace the paint pot 6 of the spray gun 1 instead of being fittedinside the paint pot. In that case, the unit 39 could be supplied as asealed cartridge 50 already filled with paint as illustrated in FIG. 14.Externally, the cartridge 50 is similar to the paint pot 6 and can beconnected to the gun 1 in the same way. Because it is sealed, however,the outlet end 51 of the cartridge must be pierced and an air ventprovided, for example at the other end 52 of the cartridge, to allowpaint to flow into the gun. The outlet end 51 of the cartridge 50 could,for example, be pierced by the user before the cartridge (with theoutlet end uppermost) is attached to the (inverted) gun. Alternatively,the gun 1 could be modified so that the outlet end 51 is piercedautomatically when the cartridge 50 is attached to the gun. An air ventat the other end 52 of the cartridge 50 could then be formed after thecartridge has been attached to the gun by piercing that end of thecartridge either manually or, for example, by attaching a separate cap53 which is designed to pierce the cartridge when it is placed inposition. Alternatively, an air vent, which simply needs to be openedwhen the gun is ready for use, could be pre-formed in the cartridge.

After use, the cartridge 50 is removed from the gun and discarded.Because the cartridge 50 contains a filter, there is no need for thesupplier to filter the paint before it is loaded into the cartridge. If,however, the paint is pre-filtered, then the filter in the cartridge 50can be omitted.

FIG. 15 illustrates an alternative form of paint pot 40 for a spray gun1, which is entirely disposable. The paint pot 40 is generally similarto the pot 30 shown in FIG. 10 except that the container 12 is replacedby a disposable container 41, described below, and the liner 13 isomitted.

The container 41 of FIG. 15 can be any conventional disposable containersuitable for containing paint and for attachment to the paint pot lid42. The container 41 may, for example, be formed from a thin plasticmaterial, preferably translucent (as shown) so that the contents of thecontainer are visible and preferably having markings 43 on the sidewalls to enable the volume of the contents of the container to bedetermined. An air hole 44 is formed in the base of the container,together with some means for closing the air hole when desired. Thatmeans may take the form of a strip of adhesive tape (not shown) which ispeeled back to open the hole 44 and can be re-adhered to close the holewhen required. Alternatively, a flip-top closure or some simplehand-operated valve mechanism may be provided. The container 41 has anexternal screw-thread at its open end, for attachment of the lid 42which is generally similar to the lid 33 of FIG. 10 and is likewiseshaped, at its upper end 42A, for attachment to a spray gun (ifnecessary by means of a suitable adapter). The lid 42 may be formed fromthe same material as the container 41 and, as shown, may also betranslucent. A flat filter mesh 45, which is also disposable, extendsacross the mouth of the container 41. The mesh 45 may be a separateitem, held at its periphery between the lid 42 and the container 41, orit may be formed integrally with the lid.

To use the pot 40, the lid 42 and filter mesh 45 are removed from thecontainer 41 which is then filled with paint (care being taken that theair hole 44 in the base of the container is closed). It is unnecessaryto strain the paint when it is put into the container 41 and, asdescribed above, it is possible to mix the paint in the containerthereby avoiding the need for a separate receptacle for that purpose.The lid 42 and mesh 45 are then put back in position on the container41, the lid 42 is attached to the (inverted) spray gun 1 which is thenreturned to its normal position, and the air hole 44 in the base of thecontainer is opened. The spray gun 1 can now be used in the usual way.On completion of the spraying operation, the air hole 44 is closed-offagain, the pot 40 is detached from the gun 1 and may then be discardedleaving only the gun to be cleaned. Before the pot 40 is detached, thespray gun 1 can be re-inverted and the trigger 5 of the gun operated toallow excess paint remaining in the gun to drain back into the pot. Ineither case, if sufficient paint remains in the pot 40, the pot could bere-sealed (instead of being discarded) and used again.

Advantageously, the container 41 of the pot is formed so that it can becollapsed after use. In some cases, it may be possible for the lid 42also to be collapsible.

As an alternative, the lid 42 could be a reusable component and would becleaned with the gun. With an arrangement of that type, it is possiblefor the disposable container 41 to be supplied as a cartridge alreadyfilled with paint and sealed by a cover which would simply be removedbefore the container is attached to the lid 42. The filter mesh 45 couldbe either a disposable or a reusable component. As a furtheralternative, the container 41 and lid 42 together could be supplied as acartridge sealed by a removable cover, at the upper end 42A of the lid,which would be removed before the cartridge is attached to the gun. Inthat form, the cartridge is similar to the cartridge 50 of FIG. 14.

Through an appropriate selection of the dimensions of the lid 42 of thepaint pot 40, it is possible for the one lid 42 to be used withcontainers 41 of different sizes. The user would then select, in eachcase, the container 41 that contains the most suitable amount of paint.It may also be desirable for a range of filters 45 having different meshsizes to be provided so that the user can select the mesh size that isbest suited to the type of paint that is being used. It is not essentialfor the filter mesh 45 to have the form and/or location shown in FIG.15: it could, for example, have a conical form as shown in FIG. 16and/or it could be located in the outlet of the lid 42, as shown in FIG.17. Alternatively, the filter 45 can be omitted if the paint is filteredbefore it is put into the container 41, or if the presence ofcontaminants in the paint is unimportant.

The lid 42 need not have the exact shape shown in FIG. 15 and could, forexample, be replaced by a push-in lid in combination with a screw-oncollar as shown in FIG. 2.

When the container 41 (with or without the lid 42) is supplied as acartridge containing paint (or other coating material) it may bedesirable in some cases for the paint/coating material to be containedwithin a sealed collapsible liner within the cartridge. That may, forexample, be desirable if it is necessary for the paint/coating materialto be kept isolated, for example from the air or from light, until ithas been sprayed onto the surface to be coated. The air hole 44 in thecontainer 41 can then remain open all the time, or may be omitted if thecontainer 41 itself is not airtight.

Depending on the shape of the container 41, it may be desirable toprovide a holder in which the container can be located to ensure that itwill not be knocked over. One suitable holder 50, shown in FIG. 18,comprises container portion 51 which is of similar shape to, butslightly larger than, the container 41 and is provided with an enlargedbase 52. The container 41 is placed in the container portion 51 toensure that it remains upright while it is being filled and/or attachedto the spray gun 1.

Although the above description refers to a paint spray gun, it should beunderstood that it applies also to other types of spray gun including,for example, guns of the type which are attached to water hoses (ratherthan air supply lines) for spraying substances such as garden chemicals.The description also applies to suction-feed guns, i.e. guns in whichthe liquid outlet from the reservoir is located at the top of thereservoir when the gun is in use and liquid is drawn from the reservoirthrough a supply tube by the action of the compressed air or otherpressurized fluid flowing through the gun. In that case, when a liner isprovided for the reservoir, the construction of the liner and/or thesupply tube should be such that the liner can collapse without blockingthe supply tube. For example, a short supply tube can be used providedall air is exhausted from the liner before the gun is used.Alternatively, a flexible supply tube could be used, which will collapsewith the liner. As a further alternative, a modified liner which doesnot have a rigid base could be used, so that the liner collapses in adifferent manner from the liner 13 of FIG. 2. Since the reservoir of asuction-feed gun is not inverted during use, as in a gravity-feed gun,it is possible to omit the air hole in the reservoir, provided theconnection between the reservoir and the gun permits air to enter thespace between the reservoir and the liner.

Returning now to the paint pot 11 of FIG. 2, the liner 13 will now bedescribed in greater detail, together with a method by which it can beproduced. The liner, shown in isolation in FIGS. 19 and 20, ispreferably transparent and is thermo-formed from a single piece ofplastics material, preferably polyethylene or polypropylene. The shapeof the liner is dictated by the internal shape of the container 12. Thecomparatively rigid base 13A is circular and the liner 13, like theinside of the container 12, is generally cylindrical but tapers inwardsslightly from the mouth towards the base 13A. The rim portion 14, likethe base, is also comparatively rigid but the side walls 13B areflexible and, as already described, can be made to collapse.Nevertheless, the liner 13 is capable of standing, unsupported, on thebase 13A with the side walls 13B extended and upright as shown in FIG.19. When the liner 13 collapses, the comparatively rigid base 13Aretains its form but moves towards the rim portion 14 of the liner as aconsequence of the collapse of the side walls 13B, as illustrated inFIG. 20. The side walls 13B collapse in a similar fashion to a plasticbag without being ruptured (e.g. by splitting, tearing or cracking).

In one form, the liner has a height of about 110 mm, a diameter at itsbase 13A of about 78 mm and a diameter at its mouth (excluding the rimportion 14) of about 86 mm. The base has a thickness of about 400 μm,the rim portion 14 has a thickness of about 900 μm, and the side walls13B have a thickness of about 150 μm. In another form, the liner has thesame height and the same diameters at its base and mouth but the basehas a thickness of about 300 μm, the rim portion has a thickness ofabout 200 μm, and the side walls 13B have a thickness in the range offrom 50 to 250 μm.

A method of producing a liner as shown in FIG. 19 will now be describedwith reference to FIG. 21( a)-(c).

A sheet 60 of low density polyethylene (LDPE), approximately 250×225 mmand 0.5 mm thick, was clamped at its periphery in the moulding frame 61of a vacuum-forming machine. The LDPE material is commercially availablefrom, for example, Plastech Extrusions Ltd. of Widnes, Cheshire, Englandand the vacuum-forming machine used was the model “FLB 725” from C. R.Clarke and Company Limited of Ammanford, Carmarthenshire, Wales. It willbe appreciated, however, that any suitable plastics material could beused and that the method could be carried out using any suitablethermo/vacuum-forming machine.

After the sheet 60 had been placed in position, the bank of heaters 62of the vacuum-forming machine was moved into position above the sheet(as shown in FIG. 21( a)), and the sheet was heated to a soft, pliable,state suitable for vacuum-forming. The fact that the sheet had reachedthe appropriate temperature could be seen by the change in itsappearance from milky to transparent.

The bank of heaters 62 was then removed and the mould platen 63 wasmoved upwards from below the sheet 60, bringing the mould 64 intocontact with the sheet to deform the latter in an upwards direction. Atthis time, the vacuum pump of the machine was switched on to remove airfrom beneath the sheet 60. The upward movement of the mould platen 63was continued until the platen reached the top of its stroke, where itseals against the frame 61 holding the sheet 60 (FIG. 21( b)). The mould64 had a shape corresponding to the internal shape of the container 12of the spray gun paint pot 11.

Operation of the vacuum pump was continued with the mould platen sealedagainst the frame 61 and the pressure difference created between theupper and lower sides of the sheet 60 caused the latter (which wasalready in contact with the top of the mould 64) to move down intocontact with the sides of the mould (FIG. 21( c)). The mould platen 63was then moved away from the cooled sheet 60 leaving a moulded portion65 having the desired shape of the liner 13 and without any pleats,corrugations, seams, joints or gussets, or any groove at the internaljunction of the side walls 13B with the base 13A. Following removal fromthe frame 61, the sheet 60 was trimmed around the mouth of the mouldedportion 65 to form the rim 14 of the liner 13. The width of the rim 14is determined by the location at which the sheet 60 is trimmed at thisstage, and can be adjusted as required.

The above-described process was found to yield a moulded portion 65 (andhence a liner 13) in which that part of the plastics sheet 60 that hadbeen in contact with the sides of the mould 64 during the formingprocess was substantially thinner than the part that had been in contactwith the top of the mould. The process differs from a conventionalvacuum-forming process which would aim to eliminate, as far as possible,any differences in thickness in the moulded portion 65 and, to that end,would include the additional step of applying air pressure to theunderneath of the heated sheet 60, after step (a) of FIG. 21, to causethe sheet to adopt a dome shape before the mould platen 63 seals againstthe frame 61: the thickness of the sheet would then be comparativelyeven when it moves into contact with the mould 64 in step (c) of FIG.21. Generally in the process illustrated in FIG. 21, for a given size ofsheet 60, the size of the mould 64 has been found to affect thethickness of the sides of the resulting liner 13 more than the base. Inother words, if the size of the mould 64 is increased, the thickness ofthe base of the resulting liner 13 will be about the same but the sidesof the liner will be much thinner. On the other hand, if the size of themould is decreased, it may be found that a point is reached at whichlongitudinal creases appear in the sides of the liner 13.

If a further reduction is required in the thickness of the sheet 60where it contacts the sides of the mould 64 in step (c) of FIG. 21, thesheet 60 can be located between two thin metal plates 66 (FIG. 22) whenit is clamped in the frame 61 of the forming machine, each metal plate66 having a hole 67 in the location of the mould 64 and larger in sizethan the largest cross-section of the mould. The plates 66 are alsoclamped in the frame 61 and the process of FIG. 21 is then repeated. Theeffect of the plates 66 is that only the central portion of the sheet 60is exposed directly to the heaters 62 and is drawn over the mould 64when the latter has been moved upwards (in this case, through the holes67 in the plates 66). In that way, less of the sheet 60 is used in theformation of the moulded portion 65 and the resulting liner 13 will havea slightly thinner base 13A and rim 14 and substantially thinner sidewalls 13B. It is also possible to obtain a comparable result by usingonly the upper plate 66 shown in FIG. 22.

As a modification of the process illustrated in FIG. 22, the plasticssheet 60 can be in the form of a circular disc of material which isclamped at its periphery between the two plates 66. Depending on thesize of the disc, the clamped periphery may then form the rim 14 of theliner 13 and there may be no excess material to be trimmed away.

It has been found that a liner 13 produced by a process as describedwith reference to FIGS. 21 and 22 will collapse as described withreference to FIG. 20 when used in the spray gun reservoir 11 of FIG. 2.The liner 13 can also be collapsed by hand by pushing the base 13A ofthe liner towards the rim 14. It has been found that the liner istypically capable of standing unsupported on its base 13A and thisfeature, although not essential to the use of the liner in the spray gunreservoir 11, may be of use for storage purposes. The liner has nopleats, corrugations, seams, joints or gussets, and no groove at theinternal junction of the side walls 13B with the base 13A: consequently,there are no internal locations in which material within the liner canbecome trapped. The base 13A of the liner will, of course, occupy somespace at the base of the container 12 of the spray gun reservoir 11 andthe markings on the wall of the container 12 need to be positioned totake account of that fact.

Although the liner 13 of FIG. 19 has been described for use specificallyin the paint pot 11 of FIG. 2, the same or a similar article can be usedin other ways (subject, if necessary to appropriate dimensionalchanges). For example, an article of the type illustrated in FIG. 19 canalso be used as a liner in many forms of receptacle other than a spraygun reservoir. It is often desirable to provide a receptacle with adisposable liner, for example to keep the receptacle clean, tofacilitate cleaning, or to protect the receptacle or its contents. Aliner of the type illustrated in FIG. 19 can be used for any of thosepurposes and is especially useful in receptacles in which substances aremixed together because there are no locations on the inside of the linerin which material can become trapped and remain unmixed.

An article of the type illustrated in FIG. 19 can, for example, be usedas a liner in a receptacle intended for paint mixing in a vehicle bodyshop, in which case it will provide an attractive alternative to thedisposable drinking cups which are often employed for that purpose.Prior to painting the repaired portion of a vehicle in a body shop, therepairer must mix-up a batch of paint of the required colour, matchingthe colour of the surrounding portion of the vehicle. The variouscomponents for a batch of paint should be measured accurately, either byvolume or by weight, into a suitable receptacle in which they are mixedtogether thoroughly before being used. If the mixing is less thanthorough, or if the receptacle is not absolutely clean, thecolour/quality of the batch of paint (and, consequently, the quality ofthe repair) may be affected.

To enable paint mixing to be carried out conveniently, but effectively,a liner of the type illustrated in FIG. 19 can be used with a measuringvessel 70 as shown in FIG. 23. The measuring vessel 70 is in the form ofa pitcher having a spout 71 in a shaped rim 72 and a handle 73. Thepitcher is provided with markings 74 on the side walls, enabling thevolume of the contents of the pitcher to be determined. Using the methodalready described with reference to FIG. 21, liners of the type shown inFIG. 19 can be produced to fit accurately inside the pitcher 70 and, byutilizing such a liner, the various components for a batch of paint canbe assembled and mixed together in the pitcher 70 without actuallycoming into contact with the latter.

A liner 75 suitable for use in the pitcher 70 is illustrated in FIG. 24.The liner 75 has a shape corresponding to the interior of the pitcher 70and is generally similar to the liner 13 illustrated in FIG. 19 exceptthat the thicker, outwardly-extending, rim portion 14 of the latter isomitted and the side walls 76 of the liner 75 include a shaped rim 77corresponding to the rim 72 and spout 71 of the pitcher. Because theliner 75 fits the inside of the pitcher 70 exactly, the possibility thatit will be punctured by the mixing implement when paint is being mixedin the pitcher is minimized. In addition, because there are no locationsin the interior of the liner in which material can become trapped, thereis no barrier to the effective mixing of all the material that ismeasured into the pitcher. When the paint has been mixed and transferredfrom the pitcher 70 (for example, to the paint pot of a spray gun), theliner 75 is removed, preferably collapsed as shown in FIG. 20, andthrown away, leaving the pitcher 70 clean and ready for further use.

Because the base 78 of the liner 75 will occupy some space at the bottomof the pitcher 70, the markings 74 on the side walls of the pitcher mayneed to be positioned to take account of that fact. It may also bedesirable, depending on the shape of the pitcher 70, to provide anextension at the top of the liner 75 which can be folded back over therim 72 of the pitcher. Alternatively, or in addition, it may bedesirable to seal the liner 75 to the pitcher 70 during use, for exampleby providing some form of shaping on the liner and the pitcher so thatthey can be snap-fitted together at the rims 77, 72.

Although it is desirable that the liner 75 of the pitcher 70 should becollapsible so that it occupies less space after use, that is notabsolutely essential. Moreover, since the shape of the liner 75 isdetermined by the shape of the interior of the receptacle 70 in which itis to be used, there may be cases in which the liner is not capable ofstanding, unsupported, outside the receptacle.

As a further alternative, an article of the type shown in FIG. 19 can beused simply as a container in which case it has the advantage that,although the walls 13B are comparable in flexibility to a plastic bag,the container will stand upright, without support, while it is beingfilled and also afterwards. The container can be of any appropriate sizeand can be used to contain many different types of items, including forexample powders and liquids, or simply as an alternative to theplastic/paper bags provided to customers by retailers. In each case, thecontainer has the advantage that there are no internal locations inwhich material within the container can become trapped. Depending on thecontents of the container, it may be desirable to be able to close thecontainer mouth, in which case some appropriate form of closure can beprovided. The closure may, for example take the form of an internal ribon the inside of the container around one half of the mouth, and amating groove also on the inside of the container around the other halfof the mouth into which the rib can be pressed to close the container.The flexibility of the container walls 13B additionally allows the wallsto be pressed down around the contents, thereby reducing the air spacewithin the container if required.

After use, when it is required to dispose of the container, the sidewalls 13B can be collapsed by hand by pushing the rim 14 towards thebase so that the container (now in the form illustrated in FIG. 20)requires less space for disposal. As already mentioned, the side walls13B collapse in a similar fashion to a plastic bag without beingruptured (e.g. by splitting, tearing or cracking).

It will be appreciated that there are many other possible uses forarticles of the type shown in FIG. 19. A liner of that type could, forexample, be used simply as a liner for a refuse bin where it would offerthe advantage of being a better fit inside the bin than a conventionalbag-shaped liner, and of being easier to handle when removed from thebin because it will stand upright on the base 13A. Similar liners couldalso be used in buckets or other containers for materials that hardencomparatively quickly (for example glue, wax or plaster): in some cases,material such as plaster is actually sold together with a mixing bucket,in which case a supply of liners could be included in the package. Insome circumstances, it might be appropriate to have a plurality ofliners, stacked one inside another, in position inside a receptacle sothat when one liner is removed the next is already in position.Moreover, since the receptacle is intended to contain a liner, it is notessential for the walls of the receptacle to be solid: the receptaclecould, for example, have the form of a framework for containing theliner.

Generally, in an article of the type shown in FIG. 19, the base 13A istypically at least 25 μm thick, more typically at least 100 μm thick.The side walls 13B are thin in comparison to the base 13A, to the extentthat they can be collapsed as described to facilitate disposal of theliner/container: typically, the thickness of the side walls 13B is lessthan half the thickness of the base 13A and may be less than one fifththe thickness of the base. Depending on the materials used, and theintended use of the liner/container, the side walls 13A will usually beless than 250 μm thick.

For certain uses of an article of the type shown in FIG. 19, the rimportion 14 may not be essential and can be omitted (as in the liner ofFIG. 24). If no rim 14 is required the sheet 60 of FIG. 21( c) would, ofcourse, be trimmed immediately adjacent the mouth of the moulded portion65. It has been found that the self-supporting nature of theliner/container can be retained even if the rim portion 14 is omitted.

It should also be noted that the base 13A of a container/liner of thetype shown in FIG. 19 need not be circular but could have another shape,for example rectangular or triangular. In the case of a liner for areceptacle, that shape may be dictated by the shape of the receptacleparticularly if the liner is required to fit the interior of the latter.In some cases, the base need not be rigid.

It will further be appreciated that the process illustrated in FIGS. 21and 22 is not restricted to the production of liners for use in thepaint pots of spray guns and can be adapted to produce liners/containersfor other purposes. It will be appreciated that the process requires themould 64 to have a slightly tapered shape with the largest cross-sectionbeing at the lower end (as seen in FIGS. 21 and 22) to allow the sheet60 to be removed when the forming operation is complete. When theprocess is used to produce of a liner which is required to fit inside acontainer, that, in turn, requires that the container should besimilarly tapered internally. The liner/container may be formed from anysuitable thermoplastic material capable of forming a thin film which isimpervious to the materials it is intended to contain. In some cases, itmay be desirable to use a material which is in the form of a laminate.For certain applications, such as food packaging, plastics with a lowgas-permeability may be preferred. For most applications, however,polyolefins such as polyethylene or polypropylene are preferred sincethese are relatively inexpensive, are readily thermo-formable, and areinert to most aqueous and organic fluids.

1. A gravity-fed spray gun comprising: a spray gun body; a fluidreservoir having a base and sidewalls, or sidewall in the case of acylindrical container, the base and sidewall(s) defining an inner cavityand a fill opening; a removable, collapsible, self-supporting liner, theliner having a base and sidewalls, or a sidewall, defining an innercavity, and a fill opening; a lid for the fill opening of the reservoirand liner, the lid having a fluid outlet adapted to connect to the spraygun body, wherein the spray gun further comprises a spray nozzle fordispensing fluid from within the liner; and wherein the liner collapseswhen fluid is withdrawn from within the liner during operation of thegun, and in which the combination of reservoir and liner has a fillopening which is inverted when connected to the spray gun body in normaloperation with fluid passing from within the liner to the spray nozzle,and wherein the liner is removable from the reservoir together with thelid, and the combination of reservoir, liner and lid is removable fromthe spray gun body.
 2. The spray gun of claim 1 further comprising aremovable filter positioned to filter fluid passing from within theliner to the spray nozzle.
 3. The spray gun of claim 2 in which thefilter is located within the reservoir and is removable from thereservoir together with the lid.
 4. The spray gun of claim 1 in whichthe outlet for fluid from within the liner to the spray nozzle is formedin the lid.